21456689 has 4 divisors (see below), whose sum is σ = 21808500. Its totient is φ = 21104880.

The previous prime is 21456667. The next prime is 21456713. The reversal of 21456689 is 98665412.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 12306064 + 9150625 = 3508^2 + 3025^2 .

It is a cyclic number.

It is not a de Polignac number, because 21456689 - 2²⁴ = 4679473 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21456629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 175814 + ... + 175935.

It is an arithmetic number, because the mean of its divisors is an integer number (5452125).

Almost surely, 2^21456689 is an apocalyptic number.

It is an amenable number.

21456689 is a deficient number, since it is larger than the sum of its proper divisors (351811).

21456689 is an equidigital number, since it uses as much as digits as its factorization.

21456689 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 351810.

The product of its digits is 103680, while the sum is 41.

The square root of 21456689 is about 4632.1365480737. The cubic root of 21456689 is about 277.8780454678.

The spelling of 21456689 in words is "twenty-one million, four hundred fifty-six thousand, six hundred eighty-nine".